China loses about a million tons of paddy caused by planthopper outbreaks annually. This is despite the huge amounts of pesticides being used by farmers. On average, Chinese rice farmers spray at least 3 times more than farmers in the Philippines. In 2005, planthopper outbreaks were very extensive in 5 provinces and some estimates show that China lost 2.8 million tons of paddy. Some researchers attributed these extraordinary outbreaks to elevated summer temperatures. Is this an expected effect of climate change? Why does China experience such high intensive outbreaks of planthoppers, which most entomologists classify as “secondary outbreaks? In the 1970s, Californian entomologists, led by Robert van den Bosch, described how agriculturalists create an insecticidal treadmill because of the new pesticides that were used extensively. Three phenomena were observed: 1) target pest resurgence, 2) secondary pest outbreaks and 3) pesticide resistance. All these are related to the increasing “pesticide addiction”. Today we see the same three phenomena occurring in highly intensive rice production systems of China, Vietnam and India.

About 35 years ago, rice intensification programs in Asia, particularly Indonesia and the Philippines, had similar experiences with rice planthoppers. Through the introduction of IPM, insecticide reduction campaigns, farmer training and policy changes to reduce pesticide use, the planthopper problem had become insignificant. Subsequently, entomological research and planthoppers in particular, began to receive lesser attention In 2005, the planthopper problem was not only serious in China, but in Japan, Vietnam, Korea and Malaysia as well and it is a wake-up call. We seem to have neglected the basic ecological principles of IPM. The key question we now need to address is “Will planthoppers become a threat to the sustainability of intensive rice systems?”. This question was addressed in a paper “Are planthopper problems due to breakdown in ecosystem services?”

The International Rice Research Institute (IRRI) initiated an international scientific discussion by organizing an International Conference, which brought together 88 scientists, agricultural directors and pesticide company representatives from Australia, Bangladesh, Cambodia, China, FAO, India, Indonesia, Japan, Korea, Laos, Malaysia, Philippines, Singapore, Taiwan, Thailand, USA and Vietnam to develop new approaches, new techniques and management tools. Report of the Conference is available.

The ecological engineering or eco-engineering approach is a new direction in sustainable pest management introduced by Professor Geoff Gurr in the Conference. The principles and examples are discussed in his book “Ecological Engineering for Pest Management” published by CABI publishing. The eco engineering approach provides a framework to strengthen essential pest management ecosystem services that will improve crop health, thus preventing secondary pest outbreaks, like planthoppers. The utilization of these principles are now being explored in Guilin, China by the Ministry of Agriculture and in Jin Hua by the Zhejiang Academy of Agricultural Sciences (ZAAS).

R. Cabunagan and IR Choi are virologists at IRRI while ER Tiongco is plant pathologist at PhilRice

Tungro in rice field, Photo credit: R. Cabunagan (IRRI)

Farmers in developing countries have difficulties managing plant diseases. Because of their limited understanding on the disease processes, the management measures they adopt are often ineffective. Since disease management has to be viewed in the context of crop production, scientists have to work with farmers to improve rice production through available management options. The measures should be simple, inexpensive and within the limited technical and financial capability of the farmers. Available technologies for rice tungro disease (RTD) are presented for farmers, researchers and extension workers in the tropics where RTD is a substantial threat in rice production.

A planthopper entomologist who has been doing research on rice planthoppers for more than 35 years in Japan, China and Indonesia.

Large variety of insecticides used in Vietnam, Photo credit: Ho Van Chien

Recently I have read an interesting book published in Japanese, entitled (in English) Neonicotinoids, Devilish Novel Pesticides and subtitled Silent Summer Without Bees, 235pp, Sangokan, Tokyo. It is written by a Japanese reporter, Syunsuke Funase, who writes on industrial pollution issues. He said in the book that he has been motivated at a young age by Rachel Carson’s “Silent Spring”.

Neonicotinoids are the class of neuro-toxic insecticides modeled after the botanical, nicotine. One such chemical is imidacloprid, a long residual insecticide used widely in rice, which is sold numerous trade names, like Admire, Confidor and Gaucho. See fact sheet.

Mr Funase paid a special attention to the colony collapse disorder (CCD) of honeybees that is affecting pollination activities and how imidacloprid may be playing a significant role in this. CCD is used to describe the abrupt and large scale collapse of beehives by massive disappearance or dying in the USA and EU where imidacloprid is commonly used in agriculture. The book discusses the loss of bees as a sign of disorders in ecosystems and the effects on human health attributed to neonicotinoid insecticides because of the long-residual and easy contamination of food and water.

The organo-phosphorous insecticides, that caused insecticide resistance in and insecticide-induced pest problems in the 1970s and 1980s are being replaced with the neonicotinoid insecticides in the 1990s. Imidacloprid had been introduced with its so called “labor-saving, environment friendly and IPM-compatible” properties and now widely adopted in Asia.

Imidacloprid was first launched as “Admire” to prevent hopperburn by brown planthopper (BPH) in Thailand as early as 1991. Since then, imidaclopriod has been widely used in the paddy fields in the Indochina Peninsula, China and Japan. Today rice planthoppers have developed multiple fold resistance to this chemical.

Imidacloprid (Chinese trade name is Pi-Chong-Lin) has also been an essential component of technical packages for high-yielding hybrid rice technologies in China. In many places, hybrid rice is being commercialized by pesticides/seeds companies together with routine insecticide applications. IRRI will need to pay attention to the ecological impacts of hybrid rice and the use of long-lasting insecticides.

The use of hybrid rice coupled with prophylactic insecticide applications can have dangerous consequences that will repeat the problems of the Green Revolution and is threatening sustainable rice production and IPM-based pest management achieved so far. Although imidacloprid has been introduced as an “IPM-compatible insecticide”, its long-lasting broad spectrum residual effects can have detrimental effects on both pollination and bio-control services.

Though traditional pest management methods such as companion planting, trap cropping and other forms of polyculture have a long history, it is only in recent years that researchers have attempted to underpin such practices with ecologically-driven research. ‘Ecological engineering’ for pest management has emerged from conservation biological control and habitat manipulation and is characterised by being based more comprehensively on ecological theory and by being developed via rigorous experimentation on the strategic use of biodiversity. Of course, the very term ‘ecological engineering’ is also provocative counterpoint to its more controversial cousin: ‘genetic engineering’. Though these two pest management approaches are not necessarily mutually exclusive, an advantage of ecological engineering is that it can be highly effective in its own right. It can, thereby, avoid the need to take the genetic engineering route with its attendant risks of consumer backlash, farmer dependence on big business and expensive inputs; maybe even environmental impact.

A recent letter to the journal, Nature, by Josef Settele of the Helmholtz Centre for Environmental Research in Germany (vol 456, page 570) made this point clearly in the context of rice pest management. Many issues will influence the decision of whether to grow genetically engineered rice commercially in China and elsewhere. Some will be emotive, such as the heightened levels of consumer concern over food safety prompted by recent melamine contamination of milk products, whilst other issues are more technical. For example, engineered rice grown experimentally performs well against moth pests such as stem borer but is completely ineffective against planthoppers which are generally far more serious pests. This illustrates a weakness of genetically engineered crops for pest management: they are effective against only certain pest types and even these pests can rapidly evolve resistance against engineered traits unless GE crops are very carefully regulated. In contrast, ecological engineering can simultaneously suppress a wide range of pests by enhancing biological control and making farms less hospitable for pest colonisation and reproduction. As Josef Settele suggests, a shift in resources to support ecological engineering could rapidly pay handsome dividends for food security.

In a report to IRRI, Ho Van Chien, director of the Southern Regional Plant Protection Center, Vietnam, stated that numerous rice fields were destroyed by planthoppers in Tan Tru district in Long An province.

Some farmers interviewed by Mr. Chien have been using 10 insecticide applications, one seed treatment, one granular application and 8 sprays. Broad spectrum pyrethroid, organo phosphates, among others, have been used in mixtures. Crops were near harvesting and yet have numerous freshly hatched nymphs which imply that the adult populations were very high after 10 sprays. It seems like the more sprays farmers use the more generations occur. Mr. Chien thinks that if farmers had not sprayed in the early crop stages, they will not have experienced such heavy attacks. Crops were sprayed when seedlings were 7-15 days old.

Hopperburn after 10 sprays

Once or twice a week in his TV program, Farmer Bridge, Mr. Chien urges farmers to avoid early season spraying but he says that his messages seem to have been completely overpowered by the more frequent pesticide advertising. Pesticide adverting messages are as frequent as one every hour in Vietnam. In addition, the pesticide company agents are organizing farmer groups, farmer field school (FFS) style teaching farmers about pesticides and giving out free samples. With the rice price so high, most farmers are anxious about their crops and companies are extending their promotion activities. Mr. Chien fears that at the present rate of excessive pesticide spraying, the Mekong Delta will once again experience huge planthopper outbreaks before or during the TET (Vietnamese New Year) holidays in late January.

In the last few years rice production in several countries has been severely reduced by insect pests called planthoppers. Besides causing crops to wilt in a condition called “hopperburn”, they also transmit virus diseases. Vietnam has lost about a million tons of rice to this menace since 2006. And in China as much as 4 million tons of rice have been lost in the same period.

Thirty scientists from Australia, China, Indonesia, Malaysia, Philippines, Vietnam and the International Rice Research Institute (IRRI) held a workshop in Ho Chi Minh City to develop sustainable strategies to manage this problem. They will develop methods that are broad based that not only build defense in the rice crop, but also defense in the surrounding areas using a new approach called “ecological engineering” pioneered by Professor Geoff Gurr of Australia. “Pests are often kept under control by many predators that live in areas surrounding rice fields. We can engineer the landscape such that these areas become homes to these predator friends”.

In opening the workshop, His Excellency, the Vice Minister of Agriculture and Rural Development of Vietnam, Dr Bui Ba Bong, expressed his special thanks to the the Asian Development Bank (ADB) and IRRI for responding to this urgent need to find sustainable solutions to the pest outbreaks. “With this project we will be able to develop management strategies that are environmentally friendly and will focus on reducing farmers’ risk of losing their crops to outbreaks”. “Very often when pest outbreaks occur, farmers use too much pesticides and we must strive to avoid this” said the Vice Minister.

The initiative was developed by IRRI and funded by the ADB. “Losses due to pest outbreaks are preventable and this project will enable scientists to use their ecological and virology knowledge, plant breeding skills and communication techniques to develop more sustainable approaches” said Dr K.L. Heong, the leader of the project. “We need to motivate thousands of farmers to conserve the predators and effective communication is essential” said Dr. M.M. Escalada, a communication scientist from the Philippines.

The pests also carry virus diseases and infected plants become discolored and stunted with no grains. “Our strategy is to develop methods to limit the spread of the viruses” said Dr I.R. Choi, a scientist at IRRI.

“One way to limit the pest population is to develop rice varieties that have resistance and we are developing new ways to incorporate these genes by plant breeding” said Dr P. Virk, a senior plant breeder at the IRRI.